As one form of a display device, a self-luminous type display device such as an organic electroluminescence display device is known. Electroluminescence is abbreviated as “EL” below. In an organic EL display device, light emitted from a light-emitting layer travels in all directions, and a part of the light is totally reflected due to a difference in refractive index between a light-emitting element and an external space (air). Most of the light that is totally reflected at an interface between the light-emitting element and the air is confined within the light-emitting element and is not extracted to the external space. For example, if the refractive index of the light-emitting layer is 1.8, approximately 20% of light emitted from the light-emitting layer is extracted to the external space, and the remaining approximately 80% light is confined within the light-emitting layer. In this way, the conventional organic EL device has a problem of low light utilization efficiency.
Patent Document 1 discloses an organic EL display device which includes a support substrate, an organic EL element provided on the support substrate, and a light reflection layer which reflects light emitted from the organic EL element. In the organic EL display device, a recess including an inclined surface along an outer edge of the organic light-emitting layer is provided in the light reflection layer. The light emitted from the organic light-emitting layer returns toward the organic EL element after being reflected by the inclined surface of the recess. According to this configuration, deterioration of image quality such as bleeding can be prevented, and the light utilization efficiency can be improved.
In general, the emission spectrum of a light-emitting material tends to have a broad distribution over a broad wavelength range. Therefore, when high color purity is required, desired color purity may not be obtained in the spectrum originally possessed by the light-emitting material. As a technique for enhancing the color purity, there has been proposed a structure in which light emitted from the light-emitting layer is multiply reflected between a pair of reflection layers to resonance, that is, a so-called micro cavity structure. When the light resonates between the pair of reflection layers, there is an effect in which the emission spectrum becomes steep around the resonance wavelength, the light intensity of the peak wavelength increases, and the color purity is enhanced. For example, Patent Document 2 discloses an organic light-emitting display device which has a lower electrode, an upper electrode, and a dielectric alternate laminated film, and includes a micro-cavity structure including the dielectric alternate laminated film and the lower electrode.